Super Mario Odyssey has co-op where you can play as Mario's hat

The Cap'n

Cappy is Mario's hat in Super Mario Odyssey that the Italian Plumber can use to control other characters by throwing it on their heads.

But in co-op, while one player is controlling Mario using a Joy-Con, player two will be invincible while acting as support. Cappy can spin into enemies and snag certain objects in the environment, allowing Super Mario to perform other actions.

It seems very similar to Sonic The Hedgehog 2 where player two could help Sonic as Tails without causing much damage when getting hit by badniks. Or even a more advanced version of Super Mario Galaxy's co-op where the second player could point a Wiimote at the screen and pick up collectables.

From around the 1:47:35 mark in the video below, you can see this being put into practice.